10 gallon kit which came with 10-15 aquatech waterfall filter. About a month in cycling process with 3 orange long fin danios which is all i wanted(for cycling) but my neice unknowingly bought me a common pleco couple days ago which is around 3 inches. my ammonia was high at first and now its pretty much at 0. The nitrites extremely high 5+ppm even though i do 40% water change everyday. Nitrates are starting to show up around 5ppm. my danios have always been swimming at the top of the water and now one is at bottom of tank barely moving. pleco seems to be fine for now ive been giving him cucumber 3 times a week (wont eat algae discs). Is there anything i should be doing differently? should i not be doing such large water changes and is it affecting my cycling process or speed? also i fill my tank to the top rim so waterline is hidden and filter water just flows in. Should i lower my water level so the filter drops from a higher point until cycling is complete?